1. Field of the Invention
The present invention relates generally to gas, oil and gas/oil fired water heaters and boilers of the type utilizing a submergible combustion chamber for supplying heat to the closed tank interior of the device.
2. Description of the Prior Art
Prior art water heaters of the type under consideration have typically provided for the flow of hot gas through a series of tubes which are mounted in vertical fashion between top and bottom support plates within the water heater tank. In this discussion, the term "water heater" will be understood to encompass both water heaters and "boilers" of the type utilized for commercial/industrial use, as well as for residential use. Water was circulated into and out of a chamber in the prior art device located between the support plates. The water contacted and circulated about the exterior of the vertical tubes to effect heat transfer to heat the water.
The typical prior art gas, oil or gas/oil fired water heater featured a non-pressurized external combustion chamber. The location of the combustion chamber on the exterior of the water heater resulted in lost heat and lower thermal efficiency. Also, the tubes and support plates were not easily accessible which generally required disassembly of the entire tank for maintenance and replacement.
In U.S. Pat. Nos. 4,465,024 and 4,545,329, both assigned to the assignee of the present invention, a water heater design was shown which featured a submergible, pressurized combustion chamber so that all combustion took place in the water heater tank interior in a chamber surrounded by water. The resulting design decreased heat loss and increased the thermal efficiency of the water heater in the range of 83% (fuel to water) and above.
In spite of the above improvements, the need continues to exist for a water heater design with a thermal efficiency exceeding that achievable with a submerged pressurized chamber alone.
The present invention has as its object to further improve the submergible combustion chamber type water heater design for increased thermal efficiency.
It is an object of the present invention to provide a water heater design of the above type which is characterized by a thermal efficiency (fuel to water) of 98% and above.